Method of treating conductors.



RICHARD JACOBY, OF BERLIN, GERMANY, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, i

A CORPORATION OF NEW YORK.

METHOD OF TREATING CONDUCTOR/S.

No Drawing.

To all whom it may concern Be it known that I, RICHARD JACOBY, a subject of the King of Prussia, residing at Berlin, Germany, have invented certain new and useful Improvements in Methods of Treating Conductors, of which the following is a specification.

My present invention relates to a method for chemically treating conductors in order to obtain certain desired physical characteristics. It is of special utility for obtaining a uniform cross-section in conductors having a non-circular cross-section inasmuch as, conductors of this nature cannot, by mechanical means, be made of so uniform a cross-section as round wires which are drawn through dies.

It has been suggested that flat strips of ductile tungsten or other refractory metals might be employed as filaments for incandescent lamps. One of the chief disadvantages of such a construction has been the difficulty of obtaining a fiat filament of uniform cross-section. To overcome this difficulty the cross-section of the filament at the smaller portions has been increased by depositing metal thereon from gas compounds. This process, however, has the disadvantage that the metal deposited from gases has properties distinctly different from those of the core, material of the wire or filament, and usually less desirable. For example, the core may be of ductile metal while the applied layer lacks this property. In carrying out my invention this difficulty is avoided because of the fact that I proceed in a fundamentally difi'erent way. Instead of depositing metal on the smaller portions of the conductor until they are of the same cross-section as the larger portions, I employ chemical means to remove metal from the larger portions until they have the same cross-section as the smallest portions. Processes have been devised for reducing the cross-section of metallic bodies by subjecting them to chemical action but in all such instances the removal of metal has been substantially uniform throughout the length of the body and consequently no gain in uniformity of cross-section has been obtained.

In the description which follows I have set forth two embodiments of my invention which are especiallv applicable to the treatment of tungsten. It will be understood, however, that I am byno means limited to Specification of Letters Patent.

Patented June 8, 1915.

Application filed April 11, 1914. Serial No. 831,281.

the particular embodiments set forth and also that my invention is applicable to the treatment of other metals than tungsten.

The first form of my invention is based upon the observation which I have made that if tungsten in a heated condition is subected to the action of hydrogen gas contaming a small percentage of oxygen that below a certain critical temperature it is attacked by the oxygen while above that temperature the reducing power of the hydrogen prevails and no oxidation. takes place; that is, for a given percentage of oxygen in the mixture there is a temperature below which the tungsten will be oxidized and above which there will be no reaction. Making use of this fact, if a wire or ribbon of varying cross-section is heated by means of an electric current the portions of the wire which have the larger cross-sec.- tion being of less resistance will be less strongly heated than the portions which have a smaller cross-section and are of higher resistance. By properly regulating the current passed through the wire the smallest portions may be brought to a temperature at which they are not attacked by the oxygen of the gaseous mixture while at the same time the larger portions remain at a lower temperature at which a portion of the metal is oxidized. As soon as oxidation takes place on the surface of the metal the resistance increases and the temperature rises and this process may be con tinued until all portions of the conductor have a uniform temperature, which is at least as great as the critical temperature, and the metal remaining has a uniform cross-section. It will be understood, of course, that in carrying out the process in this way suitable means will be employed for keeping the current passing through the conductor constant as otherwise the resistance would increase and the current decrease until the temperature of the entire conductor became less than the critical temperature. After the process has been continued long enough for the wire to reach a uniform temperature the layer of oxid which is found on certain portions of the conductor may easily be removed by any convenient method, for example, by washing in a potash solution or by subjecting the conductor to the action of hydrochloric acid gas. It may also be removed mechanically.

In the second embodiment of my invention the conductor which is to be treated is heated electrically in a fluid bath and is preferably rotated at the same time. This bath is composed of some chemical reagent which will attack the wire as, for example, nitric acid of suitable concentration. If the current is made large enough, the smallest portions of the Wire may be heated to such a temperature that by reason of the formation of gas bubbles on the surface the fluid will not attack the conductor; at the larger portions, however, the temperature will be low enough so that this formation of gas will not occur and the metal will be attacked by the fluid. As the metal in these portions is removed the resistance increases until the body reaches a temperature at which the gas bubbles will form and the reaction will then cease.

As I have before stated my invention is not limited to the treatment of tungsten but will be utilized in the case of other conductors which have a similar chemical behavior, molybdenum or tantalum, for example. It will be at once apparent to one skilled in the art that incandescent lamps whose filaments have been given a uniform cross-section in this way will be superior in many respects to those constructed with filaments having a non-uniform crosssection. It will also be apparent that my process may equally well be practised to obtain a filament which will operate at a uniform temperature throughout its length; With the usual methods of construction portions of the filament'which are in contact with bodies having a lower temperature than the filament lose their heat rapidly and hence operate at a lower temperature and efiiciency than the other portions of the filament. In some instances it may be desirable to subject the filaments to treatment according to my invention in order to reduce to a minimum the loss of efficiency due to this cooling.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. The method of obtaining metal bodies of uniform cross-section from those of nonuniform cross-section, which consists in subjecting the latter to chemical action under such conditions that the larger parts are more strongly attacked than the smaller parts, and allowing the action to continue until the metal remaining has a uniform cross-section.

2. The method which consists in subjecting a conductor of non-uniform cross-section to chemical action under such conditions that the larger parts are more strongly attacked than the smaller parts.

3. The method of obtaining filaments of uniform cross-section for incandescent lamps from those of non-uniform cross-section, which consists in subjecting the latter to chemical action under such conditions that ments of non-uniform cross-section, which consists in subjecting them to chemical action under such conditions that the larger parts of the filaments are more strongly at-f tacked than the smaller parts.

5. The method of obtaining flat tungsten if bodies of uniform cross-section from those of non-uniform cross-section, which consists in subjecting the latter to chemical action under such conditions that the larger parts of the filaments are more strongly attacked than the smaller parts and continuing the process until the metal remaining has a uniform cross-section.

6. The method of treating a metal body of non-uniform cross-section, which consists. in

passing an electric current through the same j whereby the smaller portions are vmore strongly heated than the larger portions and at the same time exposing the body to the action of a reagent which attacks the larger portions more strongly than thesmaller portions.

7. The method of treating a tungsten filament of non-uniform cross-section, which consists in passing an electric current through the same whereby the smaller portions are more strongly heated than the larger portions and at the same time exposing the filament to the action of a mixture of hydrogen and oxygen in such proportions that the larger portions of the'filament are oxidized while the smallest and most highly heated portions are not attacked by the oxygen.

8. The method of obtaining a tungsten filament of uniform cross-section from one of non-uniform cross-section, which consists in subjecting the latter to chemical action under such conditions that the larger portions of the filament are oxidized and the smallest portions are not, and continuing the process until the filament has a uniform cross-section of'non-oxidized tungsten, and then removing the oxid which has been formed.

9. The method of treating a metallic conductor, which consists in passing an electric current through the same and at the same time exposing it to the action of a reagent which attacks the cooler portions more strongly than the more highly heated portions.

10. The method of obtaining a metal body of uniform cross-section from one of nonuniform cross-section, which consists in employing chemical means to remove a part of the metal from the portions having the larger cross-section and continuing the process until the entire conductor has a uniform conductor is heated to a uniform tempera- 1o cross-section. ture.

11. The method of treating a metallic con- In Witness whereof, I have hereunto set ductor, which consists in passing an electric my hand this 20 March, 1914.

. current through the same and at the same RICHARD JACOBY time exposing it to the action of a reagent which attacks the cooler portions more Witnesses:

strongly than the more highly heated por- HANS GALEN, tions and continuing the process until the ERNST FRIEDERICH.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Iatents Washington, D. 0. 

